Invade the Dark
by ahoy-cinderella
Summary: AU / MULTI-CHAP / circa season one / what happens when Brian Cassidy gets some devastating news that turns his world upside down?
1. Chapter 1

_**Okay, so I have two new multi-chap fic ideas and I started this one first.**_  
_**I have know idea why.**_  
_**I hope you all like it.  
Any characters you recognise from the show I obviously don't own.**_

_**anyway, on with this one!**_  
_**(The title may change at some point, I'm not too sure about it.)**_

_**lyrics: near life experience - lifehouse**_

* * *

_Make this go away, I'm begging please- _  
_there's little life left here for me to bleed. _  
_Is this where I end, or is this where we begin? _

.

A few quick kisses, a swipe of his tongue across her collarbone and the soft press of his lips burnt to the spot on her lower neck along with a few harsh thrusts of his perfect toned hips and she's gone. Finally! He had spent the better part of three hours teasing her to the edge or insanity before falling back and leaving her hanging. Her body pushed hard against his as he laid his own quaking frame on top of hers, breath on breath, skin on skin, his fingers intertwined with hers, their arms pushed high above her head. Her nails dug hard into the back of his hands, his name falling from her mouth over and over again. They can spend hours teasing each other or quick minutes grabbing at each other, desperate for an orgasm.

It's never more than that.

To Olivia all this is a friends-with-benefits situation. They get together, they fuck and they go home. She fights with her over-active mind on a daily basis, he had suggested dating, only the once. She had immediately shot him down and said no, maybe a little too quickly. More and more she had been thinking about them, maybe suggesting they give it a shot but she couldn't deal with the guys at work, what would they say, what would Elliot say if he found out she was dating Cassidy? The stares, the jokes, she wasn't prepared to deal with that. Not that there was anything wrong with Brian, he was a sweet guy, she loved that she had gotten to know him better. She just wasn't prepared to sacrifice her career and her reputation just yet.

Olivia climbed from the bed, grabbing her underwear from the end of the bed and her bra from the floor, hastily shoving them back on, she felt him reach over and gently touch her hand.

"Hey…" He called softly, his voice barely above a whisper "Stay the night."

She shook her head and smiled "No, I can't…"

"Please, just tonight…" He sat up in the bed, his back against the dark-wood headboard "I won't ask again, ever again" He smiled, his eyes giving away the fake smile.

Olivia looked around, glancing at the clock indicating the early hour of the morning, her heart dropped when he started talking again.

"Or at least till I fall asleep? I've had a shitty week Liv, I honestly can't bear to watch you walk out that door again, not tonight." He mumbled sadly, little did Olivia know just how bad that week was. He shook his head and grabbed his boxers and her shirt from the floor, pulling his boxers back on he stood up from the bed.

"Forget I just said that" He laughed and handed her the shirt.

"Cassidy…"

"Don't. I'll see you tomorrow at work right?" He asked, unable to tell her he was leaving the squad. He could barely bring himself to register the news, never in his wildest imaginations did he imagined something like this would happen to him.

"Come on" She called quietly, grabbing his hand and dragging him back to bed. She pulled of her grey trousers and climbed in beside him, lying on her side.

Never had they been like this, usually it was drinks, sex and then one of them walking out. Brian had never expressed the want for her to stay, not like this.

"You look tired" She said quietly, her fingers traced the dark lines of his face, he looked exhausted. His eyes were dark, his face sunken in, had he lost weight? She hadn't paid much attention lately but lying here with him, the pale moonlight casting a faint glow over their bodies through the crack in the drapes, she noticed it all.

He smiled "You wear me out."

"There's something else." She pressed, he wasn't exactly an open book but with her he seemed freer than ever before, he had told her stories of his past, things he wouldn't tell anyone else. She felt a little guilty for not doing the same but he said he understood why.

He shook his head, his fingers tracing the sensitive skin of her upper arm making her shiver "No there isn't." He leaned forward and kissed her forehead, she felt her heart pound a little harder and her throat dry up at the feel of it; it was so romantic, just that one tiny kiss sent sparks throughout her body and he didn't even know. "Get some sleep."

She just nodded and closed her eyes.

.

Olivia felt guilty as hell as she crept around the dark bedroom, the sun barely rising in the sky. She had slept about an hour and a half before waking up and realising she wasn't in her own bed and that she had actually fallen asleep beside Brian Cassidy. They had never done it before, it wasn't a usual occurrence and she cussed herself and engraved it into her brain that it would never happen again.

She didn't want a relationship; she didn't want feelings and emotions of that calibre towards another person. She had convinced herself that she didn't need or want a lasting relationship with anyone, work came first.

She tip-toed out of the bedroom without a backwards glance, unaware that Brian was awake and heard her leave, again, he rolled his eyes and cussed himself for actually hoping that she might stay just one night, their last night together, maybe if she knew that it was the last time they would be like that she would have stayed. His mind was on over-drive, there was so much he had to do. Only Cragen knew of his situation, they had spoken about it at length just last week and had come to the conclusion that the best thing for him would be to take leave. He didn't want to, he didn't want any of this to happen but he had no choice, it was happening, to him he had never felt more alone in his life yet there was nothing he could do about it, he just had to deal with it.

.

Walking back to her desk she watched him practically stumble with exhaustion into the squad room. His eyes bleary, his body practically failing him as he almost fell into his chair. Olivia watched him drag his hands over his face and through his hair, she had left him only hours ago and he looked as if he'd been in a fight with a car, just without the bruises.

"You okay Cassidy?" She called over, taking a quick sip of her burning coffee

"Yeah, fine" He mumbled back, pulling a stack of paperwork out of his top drawer and grabbing a pen from Munch's desk.

She watched as he read and re-read papers and DD5's, trying to catch up on past cases like the rest of them. He seemed lost; his stare would wander from the stacks of paper in front of him to the windows to his computer screen. She wanted to ask, she wanted to walk over and put her arms around him, ask if everything was okay and what was bothering him. She wanted to take his pain away; the guilt ate at her with fury as she watched him cautiously walk towards Cragen's office.

.

"How are you today?" Cragen walked around to perch himself on the front of his desk.

"Fine…" Brian watched as his boss threw him a questioning look "Tired." He admitted. "Didn't sleep much last night"

"You should take the rest of the day; you can clear your stuff out if you want, while no-one's here?"

"Sounds good" He gave his boss a smile. He couldn't bear the conversations with the rest of the squad, the why's of his departure, where was he off to now? He just didn't want to face it, he wanted nothing more than to go home and sleep for a year.

"You know I'm here, we all are, whenever you need anything, just call. We take care of our own" Cragen smiled, trying to offer some comfort to the younger man sitting nervously in front of him, he was about to embark on the toughest adventure of his life and Cragen felt over-whelming guilt that he couldn't do anything, not one single thing about it.

"I know" Brian stood from the chair and held out his hand "Thanks Cap" He smiled and shook his Captains hand.

"Keep me updated, let me know what's happening, good or bad news, I wanna know." He followed Cassidy to the door "I'll check in with you, make sure you're alright"

"I'll be fine" He walked back to his desk and pulled open the drawers, the cardboard box sitting on his desk chair glaring at him, reminding him of the evil and heartache he was about to face. He didn't want to leave; he didn't want to have to put his career on hold when it was just getting started.

.

"What's going on?" He whipped round a little too fast that caused his head to spin, his heart thudding hard in his chest at the small voice questioning him. He watched Olivia's brow furrow as she watched him emptying his locker, his few personal belongings being flung into the brown box.

"I'm out." He admitted, hoping she wouldn't question him too much.

"What…why? What happened?" She came to his side, her arm gently cupping his arm, her eyes filled with concern.

"Nothing, just…this I guess. I'm not good with the vics, it's just too much." He lied, unable to tell her the truth. He didn't want her concern, her guilt, he knew she would try and help but he didn't need it, he needed to leave, figure this out for himself.

"You're great with the victims, Bri." She told him honestly, she had been in interviews with him before, he was kind, patient and he knew just how to handle a victim and a perp.

He scoffed and smiled at her "Okay" He threw a mug into the box at his side

"You are."

"It's not just that, I just…it's just too much sometimes." He spoke honestly. "Maybe I'll be better suited somewhere else." He told her.

"Well…" She started, her voice breaking slightly, her eyes felt wet and her heart tugged at the thought of not seeing him every day. "Good luck with everything" She smiled "I'll…We'll all miss you."

.

"Cassidy's left?" Olivia stood leaning against the door frame of Cragen's office at the end of the day.

"He has" Cragen watched the fleeting emotions across her face, he hadn't admitted it but he knew something was going on with her and Brian, maybe not to everyone else but to him, it was obvious.

"He didn't say anything, to any of us…" She walked in at stood behind one of the chairs, her hands clenched on the back.

"It's not an easy thing to tell people Liv, he didn't even want to tell me, I had to force it out of him"

"Not everyone can handle SVU, it's not easy…we wouldn't have thought any less of him"

Cragen looked at her confused "What…what are you talking about?" He asked, his arms perched on his desk.

"Cassidy, leaving because he couldn't handle the vics, or he thought he can't. He can, I've seen it with my own…"

"Liv…"

Olivia caught Cragen's eye, something was bothering him, he looked confused and worried. _Why is everyone keeping things from me!?_ She thought to herself.

"He didn't…that's not why he left."

"He just told me when he was packing up his…"

"Liv…"

"Cap, what the hell is going on?" She stood angrily.

"Liv, Brian's sick."

Her heart dropped to the floor, she was pretty sure her mouth was hanging open. Her body went numb and she gripped the chair harder convinced she would fall to the floor if she didn't. She could hear her heart screaming in her ears and her mouth felt as if it was stuffed with cotton wool.

"What…what are you talking about?"

"He's on leave from the force…He's sick, Liv. His doctors recommended he take leave rather as trying to work while he's on treatments. The risk of infection and stuff…it's just not worth risking his health over."

"Treatments…what…I don't..." She felt the tears filling her eyes; she was so in shock couldn't even form a full sentence.

"Liv…Brian has cancer."

* * *

**_any thoughts? _**  
**_let me know if you want more!_**


	2. Chapter 2

_When you've given into your fear_  
_When you've lost your will to fight_  
_Let me know that I can do_  
_Let me try to make it right_  
_And I will shine the light_

_._

Brian stirred from his flat out position on his couch rubbing the exhaustion from his face he grabbed his buzzing cell phone from the table

"Cassidy…" He answered dully, trying to stifle a yawn with his hand

"It's me, let me in"

"Liv…"

"Let me in, Brian"

"I'm not in the mood, Liv"

"I'm not here for that" She said quietly "Never mind, I'm in…" He faintly heard the entrance door slam behind her before she cut him off.

He didn't want to face her, not now. He quickly tidied the coffee table, getting rid of all pamphlets and advice sheets about the how's and what to expect of cancer, treatments and the side effects of the treatments. He gathered them all and threw them into the drawer of the table quickly slamming it shut before taking a quick glance around the room making sure any other signs were out of sight. He stumbled to the door upon hearing the elevator ding in the hallway, he pulled back the door and watched her approach his apartment.

"Hey" He smiled, gesturing her into his place

"Hi…" She walked in and took a look around, for the first time she was here without the expectation of sex. She stood nervously in his living room, trying to calm herself to took a few deep breaths as he fiddled around in the kitchen, she didn't want to give it away that she knew about his illness. She wanted to hear it from him.

"So, how's it going?" He handed her a mug of coffee which she gratefully accepted. Her hands wrapping tight around the mug as she sat herself down on the plush brown leather armchair at the end of the coffee table.

"Not bad, I just wanted to see what was up with you" She asked quickly "You know after the whole leaving SVU" It had been three days since he left and she had felt guilty and terrified ever since.

"I'm good. I wasn't sure I wanted to leave and then everything just kinda hit me, I realised I couldn't handle it anymore, I needed a change"

"Did it have anything to do with me?" She questioned him; he could hear the hesitation in her voice "With us?" She knew he left because of his cancer, but in the back of her mind she couldn't help but wonder if he wasn't sick, would he still have left because of her.

"No"

"You're sure?" She watched his face change; he got that same look a few nights ago when he asked her to stay the night. Like he had so much more to say, like he wanted to confide all of his secrets and trust her with the deepest parts of his heart and soul.

"I'm sure" He said quietly, quickly scoffing to cover the emotion, she could hear the feeling in his voice; it was the same on their last night together.

Olivia sat on the edge of the chair, the mug now resting gently on her knees still cradled between her hands. She watched as Brian stared off into space, his mind obviously on other things. She wanted nothing more than to walk over and pull him close, tell him everything was going to be okay and she would be with him every step of the way. She couldn't deny the feelings she had for him, she didn't want them but she had them anyway. Her heart would beat faster at the mention of his name, every time he touched her she would go numb, her mind would go blank and she would surrender her soul to him without him even having to ask. But she didn't. She had her guard up 24/7 around him, and everyone, afraid of anyone breaking down the walls she had spent years expertly building around herself. She couldn't help but wonder what would happen if she let him in, if they could have a life together and now everything had changed.

He was sick. Cancer invaded his body, this foreign being had taken over his life and ruined any chance they had at a normal relationship. She knew the last thing he would want was sympathy but she couldn't help but get emotional thinking about it, thinking about how no matter how hard he fought, she might wake up one morning and he would no longer be alive, his soul having been stolen from the world in the dead of night by a being no one could control. She would never see him again, never hear his deep, guttural laugh, be at the mercy of his boyish charm or feel his breath against her skin.

Olivia felt the panic set in and the tears fill her eyes and tried to shake it off, he hadn't yet noticed so she tried hard to keep the conversation normal.

"So where are the placing you now?" She asked, taking a gulp of the hot coffee to clear her throat

"Hmm, no idea, just waiting to hear from them" He said, sitting back against the couch, he closed his eyes and folded his hands in his lap.

"Cassidy…"

"Yeah?"

"Why did you really leave SVU?" She asked, her voice quiet, silently praying he would tell her the truth.

"I told you"

"No you didn't, not the real reason" She said quietly, giving him a knowing look, then he did something she never expected.

"I'm in love with you."

Her heart fell to the floor, splattering every ounce of emotion she had ever felt all over his apartment, her eyes widened and filled with hot unforgiving tears.

"I am so in love with you it aches. I couldn't bear to walk into that squad room every single day and see you, talk to you, laugh with you and come home and sleep with you knowing that you didn't feel the same. I should've been like any normal guy and just used you, you were offering it to me as I was to you but we clearly had different meanings behind our intentions. And I couldn't keep doing it anymore so I thought fuck it, let's quit and I'll hopefully never have to see her again." He spoke, hoping that if he terrified her enough with his feelings for her she would leave him alone. He knew she wasn't looking for a serious relationship, he knew he would always just be a quick fuck to her and if she thought he felt more she would run.

Olivia felt sick. She gripped her mug tighter unaware of how to deal with all of this. She wasn't even sure he was being honest, he never spoke so uncaring before. Maybe he was just saying this to keep himself from having to admit he had cancer, maybe all of this was lies.

"Brian…"

"You happy now?" He growled staring at her. He looked angry, beyond angry.

"Are you telling me this because you mean it or because you don't want to tell me you have cancer?" She questioned him, her voice quiet.

He sat silent in his place, his eyes widened and glazed over "Get out" He stood and thumped his mug down hard on the table, the now luke-warm contents spilling over the sides. He walked over and pulled back the door glaring at her still sitting form.

"Get out, Olivia. I didn't ask you to come here"

"You can't go through this alone" She said softly, walking towards him

"I don't want your pity. You didn't want me when I wasn't sick; don't expect me to believe you want me now."

"Brian please…"

"Don't even" He raged. "Just leave Olivia, I don't want you here."

"Brian…" She cautiously placed her hand on his toned arm

"I'm going to die!" He shouted "I am going to die. As in my heart will stop beating and I will never take another breath in this lifetime. I am going to die soon Olivia and there's not a damn fucking thing you can do about it, so please just leave me alone."

"Please don't say that…" Olivia couldn't help but let the tears fall, the last thing she wanted was to never see him again

"I don't want you around me." He gripped her arms with his hands "Seeing you hurts me more than the fact I'm going to die. You are worse for me than any cancer god could have given me. I don't want your pity, I don't want your sympathy and I don't want you." He growled furiously, she could see the tears in his livid eyes "Get out and don't come back"

She watched his arms shake as he held her away from him, she gently lifted her hands and held his wrists, she tried to ignore his words and not take them to heart, she knew he was scared and angry.

"Bri…" She carefully pulled away from his grip and slowly placed her hands on either side of his face, she watched as his anger faded to fear and the tears slowly streamed from his light, terrified eyes.

"I'm going to die" He muttered, his eyes never leaving hers

"No, you aren't…"

"Liv, I'm going to die" He whispered, his voice shaking like a scared child.

Olivia threw her arms around his neck and pulled him into a fierce hug "No. You are not going to die." She told him strongly as he crumbled into her arms.

Brian sobbed hard in her arms, his own strong arms wrapping tight around her waist, his head falling to her shoulder. She held on tight as he fell apart, there was no way she was leaving him. She reached behind her and pushed the door closed, slowly pulling back from him, she lifted his head and ran her hands through his soft dark hair.

"You are going to be okay." She stressed, pulling him with her to his couch, collapsing with him onto the cool leather.

.

"I don't want to die" He admitted.

The couple lay on the sofa; Olivia lay flat on her back, her arms around Brian's shoulders, hands running through his hair, her nails gently scraping against his scalp trying to keep him calm. He lay mostly on top of her and she welcomed the weight, she had always loved the feel of him on top of her, his body mingling with hers. He head lay on her chest; she could feel his sharp breaths against her collarbone as his hand lay softly against her ribs.

"You're not going to die, you're going to fight this thing" She told him adamantly.

"What if I can't?"

"Then I'll help you." She said "I'll be here, whenever you need anything. You can't do this alone; you need someone you can rely on"

"You're busy with work" He said quietly. "You already have thousands of victims who rely on you"

"But none of them are gonna be in my life for what I hope to be a very long time" She interrupted him, her hand reaching down to trace the rough stubble on his chin.

"No…" He pulled himself up from her but stopped when she grabbed his arms

"What?"

"No Liv, you couldn't even stay the night three days ago and now you want me for the rest of your life? Yeah right, I may be stupid but I'm not deluded."

"I never said you were."

"Don't do this to me." He whispered, his hands running over his tired face.

"I'm not doing anything Bri"

"You are completely fucking with me" His voice rising "You seriously expect me to believe that you didn't want me before and now you do? I'm damaged goods, hell I'm fucking dying Olivia"

She slapped him hard across the face "STOP SAYING THAT!" She shouted at him, her eyes once again brimming with tears.

"I am terrified" She admitted "I am terrified of having feelings beyond my control so it's easy when we don't admit stuff, keep it all locked away. It was easy for me to pretend I didn't want to be with you, I would leave, make you leave and it would be fine. And then I find out you have cancer." She sniffed, wiping the tears hastily from her face "I can't do anything about that. I can't make it better, I wish I could. I wish more than anything in the world that I could take this away from you but I can't, all I can do is try to help you through it and pray to a god I don't believe in to somehow make you better."

"Maybe this is a sign" He started, wiping his own tears from his face "Maybe we had our chance and blew it. Maybe this is god's way of punishing me for expecting more from you than you were willing to give?"

"You make it sound like we were some sordid affair." She whispered

"Could we ever have been anything more?" He smiled, trying to lighten the mood but failing.

"Oh god what if you die?" The sudden realisation hit Olivia like a ton of bricks. Her chest felt like the weight of the world was on her and she couldn't breathe, she felt her body hit full panic mode, her hands went numb and she couldn't bring herself to take a breath

"What if I never see you again? What if this is it? Oh my god please don't die." She pleaded, her hands running roughly through her own hair and down to cover her mouth "Promise me you won't leave me? Please. Brian I can't…what if we don't get a chance?"

"Hey, Liv…" He tried to reach for her but she jumped back, her body stumbling.

"God I'm so selfish…" She paced around the room "I'm so sorry, this is you having to deal with this, I'm just making it worse…"

"Liv…"

"Just please don't die." She begged "Promise me you'll fight this. I'll leave if you want me to, I'll…"

"Olivia, shut up." He interrupted her, like she did him just under an hour before and pulled her to him, her body crashing against his; he felt her light tears on his neck and soak into his shoulder through his dark NYPD t-shirt.

"I'm not leaving you" She whispered against his neck, her arms clutching him hard.

.

* * *

___**lyrics: shine the light - sugarland**_

_what do you guys think?_  
_should I keep going with this one?_

_I won't be able to update this (or any of my other stories) after Dec 5th as I'm off travelling in Australia for two months and don't think i'll be able to update while I'm away._  
_Hope you all have an amazing christmas (if you celebrate) and a brilliant new year and I'll try and get some writing done when I get back._

_Thank you for all of your amazing and continued support of my work, it means the world, you are all awesome._


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